Polyesterification of halogen containing difunctional compounds

JoumalofFluorineChemistry, 11(1981)113~126 0 Elsevier Sequoia S.A., Lausanne Received:

113

- Printed in the Netherlands

March 24, 1980

POLYESTERIFICATION OF HALOGENCONTAININGDI FUNCTIONALcm~ou~~s B,BCUTEVIN,E,B~NGALAad Y,PII%ASANTA Labohatoim

dc Ckimie

Chhn-Le de

Motiptiu,

AppLLquZe. - EcoLe Nationa& 8, ULC Eco&

The increasing

interest

in halogen containing

re-evaluate

the different

chlorinated

monomers to form polyesters.

polymers with relatively

.Sup&tie~~~~ de

Motiptie~~ C&dex [ Fhance)

Nom&e

of fluorinated

and chlorinated

of fluorinated

The use of acid chlorides

high molecular

weights diacids

and

easily

(above 3CCO). We also

in this work a new method of polytransesterification esters

polymers has led us to

methods for the polycondensation

gives

describe

from the bishydroxyethyl

at temperatures

below 2CG’C.

I~ITRCEKKTION The polycondensation derivatives physical

is presently and chemical

properties

tance to high temperatures surface

properties

to active

be stable

monomers-especially

investigation

and corrosive

chemical

reagents

and oleophobic

of aeronautics

(e.g.

under extreme conditions)

fluoro

because of the special

of these compounds which offer

such as hydrophobic

brought upon by the progress which will

of halogen containing

subject

and possess

character.

the need for

have created

excellent

resis-

specific

New requirements macromolecules

new interest

in the search for polymers which can stand a very wide temperature variation and do not become brittle reactivity

at very low temperatures

make them potential

good solid

fuel

; moreover,

binders

their

for rockets

chemical (1).

114 A bibliographic survey shows that all the classical methods of polyesterification,reactions with diacids (Z-4), acid anhydrides (5), diesters (6-8) and especially diacid chlorides (g-13), have been tried for the synthesis of these polyesters ; in each case, the halogen atoms may be present in both or in only one of the difunctional compounds. These studies show that the reaction of fluorinated diols with fluorinated or hydrocarbon acids is very difficult although after an extremely long time, low molecular weight polyesters are obtained. SCHWEICKER et al. (4) explain this low reactivity by the fact that fluorinated diols are lo4 to lo6 times more acidic than their hydrocarbon homologs, and the same reason is given for the sluggishness of transesterificationreactions of fluorinated or hydrocarbon diesters with fluorine-containingdiols ; thus, EVERS and EHLERS (6) have been unable to obtain high molecular weight polymers even under drastic conditions (reaction temperature between 200 and 3CO°C, reaction time exceeding 100 hours). The polyesterificationof fluorinated anhydrides with diols also requires very drastic conditions (3). The use of acid chlorides is the only reported method which gives satisfactory results, many polyesters have been

synthetized this way and one

may easily get polymers with an average molecular weight Mr,greater than SOOO. However, many of these results are on the one hand disparate and non conclusive, and on the other, to the best of our knowledge, only fluorinated monomers have been investigated and there is no study of chlorine containing monomers. This had led us to reconsider the three methods of polyesterificationof both chlorine and fluorine-containingmonomers : polycondensation in homogeneous solution, polycondensation in heterogeneous &i.a

(interfacialpolycondensation)and po-

lytransesterification.

RESULTS AND DISCUSSION We have used a series of chlorine-(14) and fluorine-(15) containing compounds prepared by telomerization including the diol (I) and diesters (II) and (III) :

(II) n= 2,3 ; R= nBu,CH 3

(11

CH3O2C-CC12-CH2-CHC1-CH2-CH2-CHCl-CH2-CCl2-CO2CH3 (III)

115

Each of these compounds contains function as well

; moreover, because of their as the hydroxyl

reactivity.

Finally,

two halogen atoms c( to the reactive

smetrical

structures,

the ester

of each one of these monomers have exactly

the use of both chlorofluorinated

compounds makes possible

and chlorohydrogenated

the assessment of differences

may be caused by the halogen

group

the same

in reactivity

which

OF AN ACID

DZCffLORIVE

present.

I, POLYCONDENSATION IN HCMGENOUS SOLUTION OF FLUORlNATEU

SYNTHESIS WITH

POLYESTERS

BY REACTION

A UT01

We first acid dichloride

investigated

the polycondensation

in dichlorobenzene.

of diol

It is necessary

(I) with adipic

to use an excess

of one

of the compounds in order to know unambiguously the chain ends of the polyesters.

FLORY(16) has shown that the degree of polymerization

to the excess

diol

iFn =

acceding

of the reactants

(adipoyl

When an excess according (I)

to the equation.

r+l r + 1 - 2pr

p is the extent

obtained

is related

of reaction

of the reaction

chloride)‘/(diol) of diol

(I)

to the reaction

(I))

is used,

and r the molar ratio

< 1.

a dihydroxy polyester

(IV) is

:

+ ClOC- (CH2)4-COC1 --+

HOCH2-CF2-CFH-CF2-CH2-O-(CO-(M2)4-CO-O-CH2-CF2-CFH-CF2-CH2-O)x-H

Different

reactions

The average molecular after

weight Mr, was determined by titration

in pyridine.

The &$ values

(shown in Figs.1

and 2) as will

acetylation

spectroscopy

The intrinsic 30°C in chloroform. related nearly

were run with r, equal to 0.8

viscosity The results

to the viscosity

obtained

by the Staudinger

be explained

equal to 1, and k = 2.5 x 10m3. This gives

in similar

studies,

SCHWEICKER et al.

of the chain ends further

below.

was determined at

in the table equation

; 0.97 and 1.

were checked by NMR

(n) of each polyester are collected

; 0.9

(IV)

: (4

below. Mn is

= K.m”, ; a is

: (n) cm3/g = 2.5 x 10-%n

(9) use the values

k = 3.2.10w3

;

and a = 1.

116 7

r (‘i) cm3/g

%

0.8

0.9

0.97

1

4.05

8.55

17.4

27.2

1375

2900

5900

9200

experimental Variation of (ni as a function of r for the polyester (IV) We have thus obtained

polyesters

-CF2CH20Has the end group. As stated reactive.

In order to have fluorinated

weight and the same reactivity a hydrocarbon an excess excess

alcohol

of butanediol

with comparable molecular

to prepare polyesters

chain end groups.

is necessary

alcohol,

such groups are not very

polyesters

it is necessary

group as its

di.acid chloride

with a fluorinated

previously

For this,

having

the use of

; at the end of the reaction,

an

is added :

(I) + C10C-(CH2)4-COC1 (excess) -4 Cl~-(CH~)4-CO-{O-CH2-CF2-CFH-CF2-CH2-O-CO-(CH,)4-CO}x-C1

butanediol,

HO- (CH214-O-CO- (CH2)4-C0-{0-CH2-CF2-CF~-CF2-CH2-02~- (cH~)~-CO}-O- (cH,) 4-0~

The structure

of the polyesters

were determined by NMRand by titration

and the average molecular of the end groups after

weight

acetylation.

II, POLYCONDENSATION IN HETEROGENEOUS SOLLITION We have investigated fluorinated

diacid

The polyester

chlorides

obtained

the interfacial

intensities

of the

ClOC-CF2-CFCl-CFZ-COCl (VII) with butanediol.

has the basic

structure

Figs 3 and 4 show the iWR spectra The respective

polyesterification

:

of butanediol

and polyester

of the CH2-OH (3.6 x 10m6) protons

(VIII).

and of the methy-

117

0

0 ,:

0

4

0

c;

0

d

0

u; 0

d

118 lene at the c1position of the ester groups (4.4 x 10e6) allow the calculation of Mn. The low value of the Hn obtained (1450) and the fact that the nature of the chain end groups are not precisely known limit the use of this method. From diols and acid dichlorides we have prepared fluorinated polyesters with precisely known chain end groups. The molecular weights are between loo0 and loo00 which is comparable to those obtained previously in similar studies (4)(7). However, the synthesis of acid dichlorides and fluorinated diols is very laborious and working with acid chlorides is rather hazardous. We have therefore investigated a different method for the synthesis of polyesters starting from easily obtained monomers such as (I) and (II). These monomers are easy to synthesize and to purify and are very stable.

III,

SYNTHESIS OF HALOGEN-CONTAININGPOLYESTERS BY POLYTRANSESTERIFICATION

It is surprising to see from the literature that the synthesis of halogen-containingpolyesters by transesterificationhas been so little studied. EVERS and EHLERS (6) have studied the reaction of perfluoropentandiolwith isophthaloyl chloride and various substitued isophthalic esters under drastic conditions (temperatureabove 3o0°C, reaction time < 30h) the final product is dark brown and insoluble in DMF

SCHWEICKER et al. (4) write that the

transesterificationof fluorinated diethylesterswith fluorinated diols is not a satisfactory method of synthesis. COSNELL et al. (7) have reported the polytransesterificationof diethyl malonate with hexafluoropentanediol and do not mention any special difficulty. However, to our knowledge, there is no report in the literature of the transesterificationof a halogenated diester with a hydrocarbon diol, even though this would seem to be quite practicable. We

first examined the possibility of transesterificationto

the halogenated diesters (II) and (III). This is a two-step reaction : 1) substitution of the diester group by the chosen diol 2) elimination of the substituted alcohol group which is the polycondensationstep proper. The usual catalysts for the reaction are calcium acetate for the first step and butyl orthotitanate for the second (17). The first transesterificationinvestigatedwas that of diester (II) with ethyleneglycol ; the reaction was followed by IWR spectroscopy and gas chromatography.After 30 hours at 200-220°C, a compound (IX), was formed in very small quantities :

(1x1

HO-CH2-CH2-02C-CF2-(CFCl-CF23,,-CO2-CH2-CH2OH

119 The presenceof an A2B2 systemin the 'H NMR spectrumischaracteristic of the bishydroxyethyl ester.After 72 hours,product (IX) is totallytransformed into polyester(X).

(X)

HO-CH2-CH2-O-(CO-CF2(CFC1-CF2)n-C02-CH2-CH2-O)p-H

The averagemolecularweight (byvapor pressureosmometry)is 2500. Howeveronly 20% of the diester (II)has been transformed; the natureof the diesterhas no influenceon the reactionsincewe found similarresultswith methyland n-butylesters. The same type of reactionwas carriedout with the chlorohydrogenated diester (III)and differentdiols.There is no polyesterformationwith ethyleneglycoland butanediol; instead,there is formationof dioxaneand tetrahydrofuran.To avoid the cyclizationof the diol, hexanediolwas used in excessand compound(XI)was obtainedin about 10% yield : (XI) HO-(CH2)~-O2C-CC12-CH2-CHC1-CH2-CH2-CHC1-CH2-CC12-CO2-(CH2)~-OH These reactionsshow that the first step of transesterification of fluorineor chlorinecontainingmonomersleadingto the bishydroxyalkylesters ; howeveronce this step is achieved, is very difficultand alwaysinccgnplete the polyesterification goes easilyto completion.This had led us to synthesize the bishydroxyalkylesters by a differentmethod. Saponification of the fluorine-containing diesters(II)leads to in the presenceof the corresponding diacids ; theirdirectesterification excessethyleneglycol gives the bishydroxyalkylesters (IX). The chlorine-containing diester (XII)was synthetised by directtelomerizationof 1,s hexadienewith hydroxyethyl trichloroacetate since it was impossibleto obtainthe corresponding acids by saponification becauseof their instability in a basicmedium : CC13-CO2-CH2-CH2-OH + CH2=CH-(CH2)2-CH=CH2 --+ HO-(CH2)2~O2C-CC12-CH2-CHC1-CH2-~2-CHC1-CH2-CC12-CO2-(CH2)2-OH (XII) The bishydroxyalkylesters (IX)and (XII)condensetogetherat temperaturesbelow 200°Cto give polyesters(X) and (XIII):

(XIII)

120

A titration of the end groups after acetylation gives an average molecular weight of 2500 for polyester (XIII) ; the intrinsic viscosity (n) in chloroform is 5.8 cm3/g. The polyester has a slight brown coloration ; there was no degradation and no emission of hydrochloric acid during the reaction. The product contains about 50% chlorine which may give it fireproofing properties. The bishydroxyalkylester(IX) which is a mixture of n=2 (90%) and n=3 (10%) was first heated to 190°C (0.1 tori-)without a catalyst for 2 hours. When the ethylene glycolstopped distilling off, 1% of Ti(OBu)4 by weight was added and the reaction carried on at ZOO'C for 2 hours. Fig.5 shows the G.L.C. and the Ma

spectra of the starting monomers, those of the pre-polyester without

catalyst and those of the final polyester. The G.L.C. curve shows the progressive disappearance of the two starting diesters, and the NMR, spectrum shows the transformation of the A B into an A 4 system. The relative inten2 2 sities of the signals at 3.8 and 4.6.10m6 allow the calculation of the mn of the polyester ; the same values can also be obtained form G.L.C. curve by tracing a calibration curve starting with p = 1,2,3 ... for (X,n=2).

!

31

29.8

28.6

28

461

860

1259

1658

2057

1

2

3

4

5

Ve

33.5

",

p

A value of p=2,5 mn 2 lOC0) for the prepolyester obtained without catalyst is obtained similarly. At the end of the reaction p is nearly equal to 10 (Mn = 4ooo).

CONCLUSION Polycondensationreactions from halogen-containingdiols and diesters are difficult reactions and have been little studied. SCHWEICKER and al. (4) attribute this low reactivity to the presence of two halogen atoms CYto the hydroxy function which gives them a relatively strong acid character. However, this explanation cannot apply in the case of halogen-containingdiesters, since the two halogen atoms should increase the electrophiliccharacter of the carbonyl, and increase their reactivity toward nucleophiles. We have shown this increase in reactivity of halogenated diesters in the case of reactions with amines (14).

‘-4

AI-L

5.0

4.0

ppn(6)

L_--L-u~-J Ve(nll)

30

Without

catalysis

I . , .-I Ve(m1)

30

20

20 5.0

With Ti (OBLI)~

Fig. 5. G.L.C. and N.M.R. spctra of HocH2~202ccF2~cFc1~~~,c02cH2cH20H and their polynws.

4.0

p1XiI(&)

3.0

3.0

122

The low reactivity of diesters with two halogen atoms c1to the carbonyl may be the reason for the lack of published work on polycondensationby transesterification.The method of polytransesterificationwe have proposed in this paper makes it possible to prepare under reasonably mild conditions halogencontaining polymers. The novelty of the method resides in the fact that the nature of the leaving group (ethyleneglycol)and that of the attacking group (ethyleneglycolester) are very similar ; this favors the transesterification. In this way we have prepared without major difficulty, not only fluorinated polyesters from fluorinated monomers which are very stable even at high temperatures, but we have also synthetised chlorine-containingpolyesters from chlorinated monomers which usually are not stable under the drastic conditions of

classical polycondensations.

All structures were confirmed by IR, IWR and elemental analysis. Only the main characteristics are given below, further details can be obtained from the authors. In IWR, s,d,t,m, stand for singlet, doublet, triplet and multiplet.

Preparation

of mo*omers

Diol (I) and diesters (II) and (III) were prepared according to the method described by BOUTWIN et al. (14,15,18). SYNTHESIS PIMELATE

OF 2,2,3,44,5,6,6-OCTAFLUORO-3,5-DICHLOROBISHYDROXYETHYL (IX) :

To 0,s mole of diacid obtained from the saponificationof diester (II) and 1,s mole of ethyleneglycol was added 100 to 15Ccc of chloroform. After reflux for 4h,the solution was washed with warm water to remove excess water and made neutral. After evaporation of the chloroform product (IX) was obtained in a 90% yield. IR (CHC13) : yoH : 3600 ; yc=o : 1780. N.M.R. (CDC13.10V6) : 3.9 and 4.5 (A2Bz system) ; 3.0 (s,shiftswith dilution).

SYNTHESIS

OF 2,2,4,7,9,9-HEXACHLORO

BISHYDROXYETHYL

DECANEDIOATE

(XII):

The telogen CC13-C02-CHZ-CH20H was prepared from trichloroaceticchloride and ethylene glycol. The telomerization reaction was carried as in (II) (15). Yield : 60%.

123 IR (CHC13)

: yOH

: 3600

; yCzO

: 1760 N.M.R. (CIX13.10-6) ; 2.0 (largesignal

2.55 (s) ; 3.10 (m) ; 3.9 and 4.5 (A2B2system); 4.7 (m).

Polycondensation A

POLYCONDENSATION SYNTHESIS

IN HOMOGENEOUS

SOLUTION

OF POLYESTER

Ho-CH2-CF,-CFH-CF2-~2-O-{CO-(CH2)4-CO2-CH2-CF2-CFH-CF2-CH2-O-}x-H (Iv) This synthesiswas carriedout in dichlorobenzene with an excessof diol (I),after two recrystallisations of the latterin benzene (m.p. : 69°C). as was the The adipoylchloridewas freshlydistilled(b.p. : 70-75'C/lmm) orthodichlorobenzene, the latterover P205 (b.p.: 72°/20nun). Duringthe reaction a flow of nitrogen(purifiedthroughsodiumpyrogallate, concentrated H2S04 and a colum of P205)was passed in order to removethe hydrochloric acid formedas the reactionproceeds. The diol and the diacidchloridein dichlorobenzene were heatedat 120' for 5h. The fluorinateddiol, insolublein the dichlorobenzene, disappeared as HCl, was evolved.The temperaturewas then raisedto 170-18O'Cand kept there for 15h.The mixture was then cooledconcentrated and extractedwith chloroform. It was finallydried for 48h under 0.1 torr. IR (CHC13): yoH : 3600 (weak); yczo : 1750 ; NMR(acetone-d6.10-6) : 1.8 and 2.5 (m) ; 4.56 (t ; 14Hz) ; 5.33 (m,JHF = 45Hz ; JHF = 14Hz) ; 6.5 (s). VlC gem ACETYLATION

OF POLYESTER

(IV) ; r = 0,8. zn

CALCULATION

The acetylationsolution(45mlof pyridinefor 5ml of acetic anhydride)was added to 1.95gof polyester(IV).It was refluxedfor l/Zhrand hydrolyzedat room temperature, and rinsedwith acetone.Potentiometric titration (MetrohmE 336 with automaticburette)was with 0.9M NaOH (v= 9.25~~).The volumefor the acetylatingsolutiongivesv'= 12.55~~.From these results Rn = $$!?$ = 1375 which gives an x of approximately 4 and mn of 9 according to the fonmrlamn = 2x + 1. This method givesgood resultsfor molecularweightsbelow SOOO,but above that, experimental errorsbecomegreat.

124 CALCULATION OF

OF

THE Dp,

THE ACETYLATED

OF POLYESTER

(IV) FROM

THE NMR

SPECTRUM

POLYESTER

Y

6

B

CY.

Y

E

CH3-O-CO-CHZ-CFZ-CFH-CF2-CH2-O(CO-CHZ-(CHZ)2-COZ-CHZ-CFZ-CFH-CFZ-CH2-O)x-COCH3

H protons

~

1 6 chemicalshift / / I / I Numberof H 1

B

Y

6

4.56

4.8-6.0

2.5

1.8

4x+4

x+1

4x

4x

a

E ‘

I i 2.1 6

I I

The table above showsthe differentchemicalshiftsof the acetylated polyester(IV)protons.Comparisonof the relativeintensities of the six E protonsand the 4x y protonsallowsa determination of x.

SYNTHESIS

HO-

OF POLYESTER

(CH,),-O-CO(CH2)4-CO-~O-CH2-CF2-CFH-CF2-C~2-O2~-(~~2)4-~~}-~-(~2)4-~~

This synthesiswas carriedout in dichlorobenzene solutionwith an excessof adipoylchlorideas for polyester(IV).However,after 20h, a large excessof butanediolwas added.After 5h, the polymerwas workedup as previously described. : 2 large signalsat 1.7 and 2.45.At 3.65 a not well-defined iwiR (cIKl,.lo-6) triplet; at 3.43 a singletwhich shiftswith dilution; centeredat 5.3 a triplet (J : 14Hz)and a multipletof very weak intensity.

CALCULATION

OF

THE Dp,

OF POLYESTER

(VI) FROM

ITS NMR

SPECTRUM

0. cx 8 Y 6 X Y HO-CH2-(CH2)2-CH2-0CO-CH2-(CH2)2-CH2-C02-CH2-CF2-CFH-CF2-CH2-0 xE

E 6 Y x 6 CO-CH2-(CH2) 2-CH2-C02-CH2-(CH2)2-CH2-OH Y

125

The difference (corresponding

of intensities

to the 4x y protons)

is equivalent

using Flory’s

IN HETEREGENEOUS

INTERFACIAL

TO GIVE

A slightly

basic

added to a vessel

After

C

viscous

CHLORIDE

(VII)

WITH

(VIII)

of butanediol

the diacid for

in water was carefully

chloride

in trichloro-1,1,2

ZOh, the polyester

Excess butanediol

trifluoro

formed was extracted

was distilled

oH : 1750 (strong).

off

under vacuum to

a pn

: 1.95 (large

IWR CDC13.10-6)

; 7.1 (s, shifts

; 4.43 (large)

x = 4.5 which gives

with dilution).

Calculation

of 9.

POLYTRANSESTERIFICATION

SYNTHESIS

OF POLYESTER

H-CO-(CH2)2-OJ-(CF2-CFCl)

15g of monomer (IX) was placed calcium

acetate

20 torr

for two hours and then raised

After

cooling

and antimony oxide. to room temperature,

washed with warm water and dried. polymer dried

Nm

of the butanediol. of mn =18 (19 by

liquid.

oH : 3600 ;

; 3.6 (t)

POLYESTER

standing

with ether and chloroform. give a colorless

OF DIACID

solution

containing

ethane solution.

gives

protons

the determination

(corresponding

SOLUTION

POLYMERIZATION

BUTANEDIOL

IR (CDC13) :

allows

at 1.7.10V6

at 2.45

formula).

POLYMERIZATION

signal) ‘

and the signals

to the 8 central

Comparison with the 4x c1 protons

B

between the signals

to the 4x+8 6 protons)

(cDCl,.lo-6)

at 10-l

torr

G.L.C. ;ere detector

with 0.1% by weight of

The chloroform

was distilled

in chloroform, off

and the

hours.

(A2B2 system)

; 4.7 (s, A4 system).

determined with a WATER8Associates was used.

) -OH

was heated at 180°C under -1 torr for one hour. to 2CQ’C under 10

the polymer, was dissolved

100,500 and 1ooOA columns. The solvent refractometer

in a reactor

-O(CH

The reaction

for several

: 3.9 and 4.5

-CF -CO)-) z-2-x-2-2p

Apparatus with 100,

was THE, at Zml/mn and a differential

(x)

126 SYNTHESIS

OF CHLORINE-CONTAINING

POLYESTER

(XIII)

H-~O-(CHZ)~-OZC-CC12-CHZ-CHC1-CH2-CH~-CIIZ-CHC1-CH2-CC1Z-CO~x-0-(CHZ)2-OH L The synthesis

NMR (CDC13.10-6) 4.5 (m)

was carried

: 2.0 (large signal)

The potentiometric of polyester

of the acetylating

; 3.1 (m) ; 3.9 and 4.3 (A& i

system)

;

E.L. COTTRIL

titration

method mentioned

which

in chloroform

leads to M

2

R.FILLER,J.F.O'BRIEN,J.V.FENNER

3

M.HAUPTSTEIN,C.S.STOKES

4

G.C.SCHWEICKER

= 2332.

gives for (q; = 5.8Occ/g.

and J.GREEN,C.A.72,81004r

and

(page 13) for the

(IV) gives with v = 8.5~~ of 0.98N NaOH, v'= 10.25~~

solution,

Viscosity

5

(X).

; 4.6 (s, A4 system).

acetylation

1

out as for polyester

(U.S.Patent

3 493 546,(1970)).

and M.HAUPTSTEIN,J.Amer.Chem.Soc.,E,966,

and C.NODIFF,J.Amer.Chem.Soc.,fi,4005,(1952).

P.ROBITSCHEK,J.Polym.Sci.,2~,33,(1957).

M.HAUPTSTEIN,J.F.O'BRIEN,C.S.STOKES

and J.R.FILLER,J.Amer.Chem.Soc.,

z,87,(1953). 6

R.C.EVERS

and F.L.G.EHLERS,J.Polym.Sci.,1(10)3020,(1969).

7

R.GOSNELL

and J.HOLLANDER,J.Macromol.Sci.Phys.,B1(4),831,(1967).

8

K.C.SMELTZ

9

and G.CREST,U.S.Patent

F.V.GOUINLOK,J.R.and

3 504 016,197O.

C.J.VERVANICandG.C.SCHWEICKER,J.Polymer.Sci.,

!(3),361,(1959). 10

L.W.ALEXANDER,V.C.R.McLOUGHLIN

and J.THROWER,Brit.Patent

11

I.M.DOLGOPOL'SKII

12

G.C.SCHWEICKER

13

KH.A.DOBINAand

14

B.BOUTEVIN,E.B.DONGALA

15

B.BOUTEVIN

16

P.J.FLORY,J.Amer.Chem.Soc.,62,1057,(1940).

17

J.P.HUET,ThPse

18

E.B.DONGALA,These

1 261 504,(1970)

andKH.A.DOBINA,Vysokomol.Soyed.L,1540,(1967).

and P.ROBISTSHEK,U.S.Patent

3 016 361,(1962).

I.M.DOLGOPOL'SKII,Vysokomol.Soyed,~,A13,(l97l)~ and Y.PIETRASANTA,Europ.Polym.J.13,939,(1977).

and Y.PIETRASANTA,Europ.Polym.J.,12,283-286,(1976).

Doctorat

d'Etat,Rouen,(1974).

Doctorat

d'Etat,Montpellier,(1977).

1953)